Refracting and diffusing container for incandescent lights.



. cent lamps.

PETER COOPER EEWITT, or EINGwooD M ANoE, NEw-JEESEE.

REFRACTING AND DIFFUSING CONTAINER FDR IN CANDSCENT LIGHTS.

Specification of Iietters Patent.

Patented Mar. 28, 1916.

Application filed aluly 9, 1912. Serial No. 708,421.

To all whom 'it may concern.' y

Be 1t known that I, le'rnn CoorER HEwiTna citizen of the United States, and

ers for Incandescent Lights, of which then following is a specification.

My invention is especially V'appli able for use in connection with a source emitting more light in one direction than in another such, for instance, as an incandescent lamp having a filament constituting a linear source of light, and the object of my invention is to provide means for changing the direction of light rays from-such a source so as to permit the better illumination of objects in a desired direction from the lamps, and also to secure by diffusion a. softening of the light. i

In my prior application, Serial No. 619,733, filed April 8, 1911, and my prior Patent No. 1,036,524, issued August 20, 1912, I have disclosed and claimed an invention of mine pai'- ticularly applicable to the ordinary commercial tungsten filament andjother incandes- In the preferred embodiment I disclose the use of etched groove-like markings on the? bulb so narrow and so closely spaced that when viewed from ordinary distances, rays from any given length of filament, separately scatteredY laterally by each of a multiplicity of the groove-like markings, blendrin the field of illumination, and cause said'length of filament to have the optical appearance of a widened band; or transversely continuous surface of light, the

-width of which is practically independent of the diameter of the filament, but lis dependent upon the shape, angle and spacing of the effectively contributing groove-like markings. In my present form the groovelike markings and the filament lengths are so disposed in respect to each other that said groove-likemarkings serve as refractors to direct the light to points deficient in luminosty, and, at the same time, the filament lengths are each apparently widened out so as to produce upon theeye of the observer, the effect of a single substantially continuous fiame or cloud of light inside of the container, or the effect of a continuous lightgiving surface, or both, although the distribution of light in the various parts of said fiame cloud or surface may vary in intensity; The appearance thus given, of a single continuous blaze of light emitted through a wide area may-include the whole or a large portion of the surface of the whole and the luminous cloud may appear as though filling the whole or a large part of the interior of the globe. The refraction may be in the direction desired.

In my prior patent, I have 'made it clear that the lateral light dispersing action of the minute closely-spaced grooves is practically effective through a wide angle on each Yside of parallelism of apparent pmjected lengths of groove and filament, and I have described an arrangement in which grooves, disposed in planes passing through the major axis of the lamp, act effectively with respect to zig-zag lengths Vof filament which slant in opposite directions at wide angles lfrom the Ydirection of the groove without materially or noticeably decreasing the optical effect of widening of each length of filament to a widened band or ribbon of llght or widening the groups of such lengths of filament to form a blaze of light. From this it will be evident that the principal practice or commercial value of the longitudinal arrangement of grooves is that of locating the wide blaze of light at substantially right angles tothe axis of the lamp, thereby satisfying the sense of order and symmetry of the observer. In this connection, I wish to call particular attention to the fact that the widening eHect being dependent upon the number and spacing of the effectively contributing grooves, the amount of widening :of Ythe ribbon or blaze is not a percentage widening but is a definite distance. For instance, as an illustration, if the blaze of light fro-m a group of zig-zag filaments is one inch wider Ithan the projected width of the group (that is, half an inch on each side) the widened ribbon produced by each individual length of filament will also be one inch' wide or one-half inch on each side. The, widening procurable by my basic invention is relativelyenormous n(as, for instance, a filament one thousandth of an inch in diameter being widened to a ribbon of light one inch in diameter), and I have found in practice of my present inventio-n on incandescent bulbs, that the projected angle of groove to the filament can he increased up within, say, 10 to 15 degrees of a right-angle and yet the widening effect on each filament will'still be,say, about 011efourth of an inch, or say 250 times its diameter by suitably proportio-ning the depth to the width of the groove; even less widening than the above is amply sufficient in the commercial lamp to produce a great softening effect and can produce the effect of a continuous surface of light or blaze from onek or more lengths of filaments. The precaution to be Observed in connection with such wide angle use of the grooves is that so far as concerns the optical effect of lateral widening of thel lament, the effective steepness of the sides of the grooves must be considered as decreased' and their distance apart as increased as the groove departs from parallelism with the projected length of the filament, the effective steepness and spacing of the grooves being determined by their4 section along a plane at right angles to the apparent or projected length of the filament. When the grooves are at right angles to this plane (that is, when projected lengths of .groove and filament appear parallel), the grooves are effectively steepest and closest together and have the maximum widening effect. On the other hand, when grooves or portions of grooves on a surface parallel to the filament lie exactly in the right angle plane, its widening effect is theoretically zero if they form a perfect refractor, because in such case the refraction laterally of the grooves being lengthwise of the filament, is not optically evident as widening but appears as lengthening. Pursuant to these principles, I have discovered that by making the grooves sufficiently steep-sided and corresponding closely spaced as they must be to get the steep-sidedness necessary on the commercial blown bulb, the grooves may in practice be arranged diagonally or owing to thecurvature of the bulb and irregularity of the filament lengths, even at right angles to the general direction or common axis about which the lengths of filament are arranged. Even though a considerable portion of some one filament may appear ineffectively widened from certain view points, nevertheless, if the grooves are sufficiently steep-sided and sufficiently closely spaced, a large proportion of the total zigzag filamentary lengths will be at such angles as to be effectively widened and productive of a practically continuous surface of light. This is attainable through practically polished groove-like markings closely spaced and arranged at right angles to the `axis of the lamp, and hence, not more than,

say, 10 to 25 from right angles to the projected length of some portions of vsome of the lengths of filament. TheJ slight irregularities in cross sectional formation and lateral spacing of the grooves due to inaccuracies of the ruling or action of the acid, contribute to this same result. By the term polished, I mean transparent in contradistinction to frosted or opaque. In other words, a surface in which thereis no material loss of light by absorption or complete reflection.

Y A filament or any other linear source of light emits the largest portion of its light in a direction substantially at right angles to its length and objects in y'alinement therewith are not illuminated to the saine extent as those at `one side thereof. Even in the common type of tungsten incandescent lamp, where the filaments are arranged zig-zag, they extend in the same general direction and most of the light is transmitted in a direction at right angles to the axis of the container and the space at Ithe ends of the container receive very little light. Grooves on the bulb parallel with its axis have but little effect in correcting this and my present invention contemplates the arranging of the markings at an angle to the general direction of the filaments and the proportioning of the steepsidedness and close spacing of the grooves to the angle of the projected length of the grooves with..the projected length of the rilament, so that I am able to effectively use 'my invention, first, vto produce a highly useful directive action, and, second, to produce diffusion of the light, thereby producing a softening of the intrinsic brilliancy of the source by a lateral widening effect of a filament, whereby by availing of both the light is not only diffused and its intensity decreased, but the direction of the deflection is in a desired direction and may be directed toward the wellknown dark spots 'or zones which in ordinary lamps are formed adjacent the projected longitudinal axis of the filaments and lamp.

I have found that it is not so practical to mold or cut grooves fine enough and closely spaced enough on bulbs of the present commercial thinness of wall as to produce the grooves by using hydrofluoric acid in accordance withmy prior invention. I can etch grooves of the required fineness, form, steep-sidedness and polish necessary .for the above described high angle arrangement with respect to the projected lengths of the filament and for the direction of the light.

In the employment of my invention, a large portion of the light from an incandescent lamp supported overhead with substantially vertical filaments may be directed downwardly, and at the same time may be softened by avery eective lateral component of the light-refracting effect of the grooves. By arranging the markings with each having a material component at-right angles to the general direction of the filament, most of the light rays from any point on the source will be refracted so that they diverge in a plane at right angles to the groove-like markings or ridges on the surface of -mination.

container. If these extend around the container in a general direction at right angles to the series of filaments. the light may be given a strong downward component, such component depending on the steep sidedness'of the refractors and the angle the interior surface makes with the filament, and made to shed light on the normal dark spots of the bulb.

If the bulb or other container be spherical or otherwise formed with equal portions of the vertical filament orother source of light above and below the plane of the maximuni diameter Aof the container. and tl1e.refractors or prism-like bodies formed by the markings encircle the source of light either in concentric circles or concentric helixes.

angle of the inner surface to the filamentl` toward both ends of the container, and the.

light rays emitted will be divided into two portions which will be refracted away from each other upon opposite sides of the plane of lnaximum diameter of the bulb.y Thus objects at each end of the bulbor other container will be illuminated to a higher degree than they would were the surface plane. If the bulb or other container beI suspended in an overhead position objects below the bulb will be illuminated as well as those at the sides and there will be a more uniform distribution of light.

A bulb or other container constructed in accordance with my invention and having an equal -directing action in two directions may be utilized for uniform spherical illu- In ordinary practice, I prefer constructing the bulb or other container, so that there will be a much-larger directive action toward one end of the bulb than toward the other, which renders the4 use of a reiector unnecessary. This I accomplish by. placing all or almajor portion of the filament or other source of light on the same side of the plane of the major transverse diameter of the bulb. Thus the larger portion of the light rays Jtraveling laterally from the filament or other source Will strike the wall of the container at an ailgle to ther inner surface as in the lower half of case above stated. Thus more of the light will be directed in one direction than in thei other, and in this case given, a downward direction will result.` The nearer the shape of the con-- tainer approaches that of a cone, the larger will be Vthe amount of light directed away from the plane of the base and in the general direction of the apex of the cone.

It is not essential that the grooves be absolutely uniform as slight irregularities inthe width, shape and depthof the grooves may be Apresent without materially modifying the different` refractive power than those oppoi site the center of the filament. Thus suc'- cessve grooves or markings lnay be varied to secure a more effective distributing or directing action. Although the most effective directing action will be produced when the grooves lie in planes at right angles to the linear source of light. vet a very effective and highly desirable directing action toward the ends of.the bulb may be produced with the prisms disposed helically around the bulb. Under certain circun-lstances, it may be desirable to have the lines or markings running in different directions and different angles on .different parts of the container, so as`.to accentuate or modifythe directive action.

By etching the grooves extremely na'rrow, I am able to secure the desired steepsidedness without cutting thegrooves to an may the etching or other glass-removing operation be accomplished.

In the accompanymg drz'iwmgs, forlmng a part of this application, Figure 1 is a side elevation of an incandescent lamp o f .sub-

stantially spherical form and having the groove-like markings extending around the lamp substantially at right angles to theaxis thereof; Fig. 2 is a side elevation of a lamp having the filaments disposed entirely at one side of the transverse plane of maximum diameter andmarked similarly to the form shownin Fig. y1; and Fig. 3 is a side eleva-A tion of the ordinary pear-shaped incandescent light. having the. markings helically disposed and with the major portion of the separate flamentary lengths below the plane of maximum diameter.

In carrying out my invention, I lpreferably utilize the -xordinary commercial incandescent electric lamp, but it is not Vlimited to any particular form or type of construction. In the drawings, I have illustrated .in l, a lamp having asubstantially spherical body of blown glass and of commercial thinness. Vithin the bulb is supported the light-emitting filament, which maybe arranged in zigzag form and supported upon arms as in the ordinary tungsten lamp of commerce, or may be supported as in the ordinary carbon filament lamp.

.The form and arrangement of'the filament does not involve any feature of my invention,l except in so far as the relativelpositioning and direction of the filamentary lengths and the light-deliecting grooves or markings on the surface are concerned. The lamps illustrated have the filaments extending in the same general direction as the major or longitudinal axis of the bulb..

Upon the outer surface of the bulb, I'provide minute ridges or grooves 11, which extend in the direction having a material component at right angles to the projected lengths of the filaments. These grooves or ridges are very minuteA and are closely spaced, and their sides are of such -steepness as to give a material light-directing action at an angle to the general direction of the grooves. These grooves or v'ridges may be formed in various different ways, as, for instance, molding, cutting, grinding or sandblasting, but are preferably formed by coating the outer surface of the bulb with a fine skin of wax, asphaltum, or other similar acid-resisting material, and then cutting or scratching through the wax for the purpose of exposing the surface of the glass along lines properly spaced and of suitable width. The bulb may then be immersed in hydrofiuoric acid, in desired form, condition, dilution or admixture, for the proper length of time, or in place of hydrofluoric acid solution, the bulb may be exposed to hydrofluoric gas. Upon subjecting the bulb to the action of the chemical for the proper length of time and then cleaning off the remaining wax, the operation will be completed. This method of forming the grooves is substan.\

tially the same as disclosed in my prior applications above referred to.

The grooves may be made aslarge as onev thirtieth of an inch or even larger, and as small as one-two hundred and fiftieth of an inch or smaller, from center to center depending on the use designed for and prac-- tical reasons of economy and manufacture,

and may be of any desired shape in cross section dependent upon the permissible depth to which'the glass may be etched, the degree of directing action which it is desired to secure, and the steep-sidedness necessary to secure the optical appearance of a widened band as the projected lengths of the grooves and/filaments approach the 4,rightangular position. The action of the acid is so controlled that the surfaces of the grooves v are substantiallyy smooth or polished, so that there is practically none ofthe loss which markings at a high angle to the projected' occurs in the ordinary frosted bulb. The essential feature of my present invention involves the forming of these groove-like lengths of the filaments, in order that the surfaces of the grooves may give a lightdirecting action in the direction of the projected lengths of the filaments. With the filaments extending in the'same general direction as the major or longitudinal axis of the bulb, I may form the markings around the bulb at substantially right angles to the longitudinal axis, as is shown in Figs. 1 and 2. The small ridges of glass between adjacent grooves act as prisms and refract the light rays laterally from the outer angle or edge of the prism. Thus, each light ray in traveling outwardly at right angles to the filament will be bent toward either one end or the other of the bulb. With the bulb substantially spherical, as shown in Fig. 1 and with the filaments positioned opposite to the major diameter of the bulb, there will be an equal light-deflecting action toward both ends of the bulbs.

If it is desired to secure a larger lightdirecting action toward one end than toward the other, for instance, on a bulb which is to be supported overheadl and illuminate objects beneath it, I may employ the bulb 12 apex and a larger portion of the light rays traveling outwardly'at right angles to they filaments, will be directed in the general direction of' the apex of the bulb than will be directed toward the flatter end or base.

Substantially the same results may be secured by employing a bulb 13 of the ordinary commercial form, as shown in Fig. 3. In this case, the major portion of the bulb walls are inclined inwardly toward the socket instead of toward the tip `as in Fig. 2. In this form, I have illustrated the groovelike markings arranged helically, so that the angle between the grooves and the projected lengths of the filaments will be not quite as great as in the annular arrangement of markings'shown in Figs.'1 and 2. The inclination or pitch of the grooves may be varied at will,but the greater the angle between the projected length of groovesl and filaments, the greater will be the directing action in the general direction of the lengths of the filaments. The grooves may extend into the bulb symmetrically to the surface,

or all or a portion of the grooves may eX- positions 1n the bulb, it is evident that even with the grooves encircling the bulb in plane" at right angles to the major axis, few, if any. of the grooves and projected lengths of filaments will be exactly at right angles, andthus by making the grooves with given length of lament sufficient steep sidedness, the rays from any will be separately scattered laterally by each of a multiplicity of groove-like markings andvwill blend in the field of illumination. Each length of filament will have not only the optical appearance of a widened band or transversely@ continuous surface of light, but each of said bands may appear elongated substantially to the tip of the bulb, andthe bulb when viewed from the end may present a substantially uniform field 0f illumination` closely approximating the illumination at the sides of the bulb. If the filaments be arranged 1n some other form than -in the general direction of the length -of the bulb, it is evident that the direction of the groove-like markings may be correspondingly varied to secure the like results, and

with other forms of light be modified accordingly.

Having thus described my invention, Il

claim as new and desire to 'secure by Letters Patent:

1. An incandescent electric lamp of the filament type, having a blown bulb of commercial thinness symmetrical in respectto its major axis, said bulb having a plain interior surface and having formed on the ex-V terior surface thereof a multiplicity of narrow, concave, closely spaced groovesV extending around the bulb approximately at right angles t0 said major axis, and of a depth less than one-half the thiclmess of the glass and spaced with their centers not more than v one-iiftieth of an inch apart, the surfaces ofsaid grooves being smooth and the ridges between said grooves forming refractors of 7 such steep-sidedness as to deflecting action in the major axis of the bulb.

give effective light direction of said its major axis, said bulb having a plain interior surface and having etched on the exterior surface thereofaJ multiplicity of narrow, concave, closely spaced grooves extending around the bulb approximately parallel with each other and at a high angle to said major axis, and of a depth less than one-half the thickness of the glass and spaced with their centers not more than oneiftieth of an inch apart, the surfaces "of said grooves being smooth and ,the ridges between said grooves forming refractors of such steep-sidedness as to give effective light deflecting action in the direction of said major axis of the bulb.

3. An incandescent electric lamp of the filament type, having 'a blown bulb of commercial thinness symmetrical in respect to its major axis,said bulb having a plain interior surface and having etched on the exterior surface thereof a multiplicity of nar-l row, concave, closely spaced grooves exf allel with eachother and at a high ang e to said majorl axls, and of a depth less thany one-'half the thickness of the glass and spaced with their centers not more than oneiftieth ofv an inch apart, the surfaces of said grooves being smooth and the sides of adjacent grooves meeting to form knife edged ridges. y y

Signed at New York c1ty`1n the county of York uthis New York and State of New eighth day of July, A. D. 1912.

t PETER COOPER A`Witnesses:

CLAIR-W. FAIRBANKS, IRVING M, OlxsnmGH'r. 

